Normal Electrocardiogram Lecture Objectives

The electrocardiogram (ECG) records the mechanical activity of the heart on special paper.

ECG stands for Electrocardiograph, not Electrocardiogram.

The contraction and relaxation of cardiac muscle is a result of hyperpolarization and depolarization of myocardial cells.

The 12-lead ECG is composed of two lead systems: standard limb leads and chest leads.

The electrodes pick up electrical forces from the surface of the body and record them in the form of an ECG.

The 12-lead ECG includes limb leads I, II, III, aVR, aVL, and aVF.

Precordial leads are obtained from electrodes placed on the chest in designated areas.

The ECG paper speed is usually 50 mm/sec.

The standard calibration on ECG paper is 5 mm (5 small boxes) equal to 1 mV.

The QRS complex represents the repolarization of the ventricles.

In standard limb leads, one limb carries a negative electrode and the other limb carries a positive electrode.

Augmented limb leads are also called bipolar leads.